Method and apparatus for moderating the temperature of an internal combustion engine of a motor vehicle

ABSTRACT

In an internal combustion engine of a motor vehicle, in order to shorten the cold-starting phase, it is provided that upon a shut off of the engine, essentially the entire amount of coolant is pumped out of a cooling system into a normally empty heat insulated reservoir, from which the coolant is fed back into the cooling system again upon subsequent start up of the engine.

FIELD OF THE PRESENT INVENTION

The invention relates to a method for tempering an internal combustionengine of a motor vehicle, to which a cooling system with a coolantcirculation for liquid coolant is assigned, and to a cooling system forthe internal combustion engine.

BACKGROUND OF THE PRESENT INVENTION

After a cold start, until it reaches its operating temperature, aninternal combustion engine has relatively poor properties, such as therelease of major quantities of pollutants and high friction and hencewear. The deficiencies of a cold start can be avoided by adequatelypreheating the engine. The means proposed in the past for this purpose,particularly latent heat exchangers or heat insulated reservoirs builtinto the cooling systems, have so far not been deemed practical.

German Patent Disclosure DE 1451890, discloses the use of a pressureequalizing or venting tank as a reservoir, which communicates with theintake side of a coolant pump via a bypass line that can be blocked offby a blocking device. During normal operation, the coolant circulatesthrough the venting tank. Upon a shut off of the engine, the blockingdevice is dosed to retain coolant in the reservoir, and it is openedupon engine starting, with the coolant from the tank being initiallywarmer than the rest of the coolant in the cooling system.

SUMMARY OF THE PRESENT INVENTION

The object of the invention is to enable preheating of an internalcombustion engine in a cold start without having to increase thequantity of coolant in the cooling system.

This object is attained by feeding the coolant of the cooling systeminto a normally empty heat insulated reservoir upon a shut off of theengine, with essentially the entire amount of coolant in the coolingsystem being pumped into the reservoir, from which the coolant is laterfed back into the cooling system upon subsequent start up of the engine.

As the reservoir is normally empty, no extra coolant is necessary toaccommodate the reservoir and, therefore, so that the weight of thevehicle is not significantly increased. Also, the normally emptyreservoir allows substantially the entire amount of coolant to be pumpedinto the reservoir, so that no coolant remains unused in the coolingsystem, thereby maintaining the temperature of the coolant that preheatsthe engine relatively high.

In a further feature of the invention, it is provided that a heatexchanger for a passenger compartment heating system and/or a heatexchanger for a transmission fluid cooling system and/or a heatexchanger for a motor oil cooling system is disposed in the coolingsystem, and the coolant is pumped from this entire cooling system intoand out of the reservoir.

Briefly described, the method of the present invention is a method formoderating the temperature of an internal combustion engine of a motorvehicle during start up of the engine after the engine had previouslybeen shut off, using a cooling system that circulates liquid coolantthrough the engine. The method of the present invention includes feedingthe liquid coolant from the cooling system to a normally empty heatinsulated reservoir upon shutting off the engine. Upon subsequent startup of the engine, the coolant in the reservoir is fed back to thecooling system. Preferably, substantially all of the liquid coolant isfed from the cooling system to the reservoir.

In the preferred embodiment, the feeding of coolant to the reservoir andthe feeding of coolant from the reservoir is temporarily delayed.

In a preferred embodiment, the cooling system includes a passengercompartment heating system, a transmission fluid cooling system and amotor oil cooling system, and the liquid from the reservoir is fed toone or more or all of these systems. This feeding may be in any desiredstaggered delay sequence.

If desired, the feeding of liquid from the reservoir to the coolingsystem may temporarily bypass the radiator of the engine cooling system.

Briefly described, the apparatus of the present invention is a reservoirsystem used in conjunction with a cooling system for an internalcombustion engine of a motor vehicle which has a conduit through whichthe liquid coolant is circulated between a radiator and an engine. Thereservoir system includes a normally empty heat insulated reservoir, areservoir conduit connecting the cooling system conduit with thereservoir, a pump in the reservoir conduit operable upon shut off of theengine to feed the liquid coolant from the cooling system into thereservoir. A valve in the reservoir conduit is operable upon start up ofthe engine for feeding of the liquid coolant from the reservoir into thecooling system. Preferably the reservoir has a capacity for containingsubstantially all of the liquid coolant in the cooling system.

In the preferred embodiment, the cooling system includes at least one ofa passenger compartment heating system, a transmission fluid coolingsystem and a motor oil cooling system, and the reservoir system includesa return conduit connecting the reservoir to these heating and coolingsystems. In this embodiment, the reservoir has a capacity for containingsubstantially all of the liquid coolant from these systems. Preferably apump and a normally dosed valve are located in the return conduit andare operable upon start up of the engine to feed the coolant liquid fromthe reservoir to these systems.

If desired, a temperature sensitive bypass control valve may be locatedin the cooling system conduit upstream of the radiator to selectivelydivert the flow of coolant liquid from the reservoir to bypass theradiator and recirculate the cooling liquid to the engine.

Preferably, the reservoir is positioned at a level higher than theradiator and engine so that the cooling liquid may be fed from thereservoir by gravity.

Preferably there is a valve in the reservoir conduit that is operable tonormally permit flow of liquid coolant to the reservoir and to preventbackflow. This valve is also openable upon start up of the engine topermit backflow of liquid coolant from the reservoir to the coolingsystem.

Also preferably, the reservoir conduit is connected to the coolingsystem conduit upstream of a cooling system pump that pumps coolant tothe engine.

In the preferred embodiment, a pressure equalizing or vent tank isconnected to the reservoir for passage of air thereto from the reservoiras coolant liquid is fed to the reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, embodiments, and advantages of the present inventionwill become apparent from the following detailed description withreference- to the drawings, wherein:

FIG. 1 is a schematic illustration of a cooling system according to apreferred embodiment of the present invention; and

FIG. 2 is a schematic illustration of a cooling system according toanother preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The internal combustion engine 10 shown in FIG. 1 is located with aradiator 11 in a cooling system. A pump 12 pumps coolant to the engine10 via a cooling system conduit 13. The coolant leaving the engine 10flows to the inlet to the radiator 11 via a conduit 14. A bypass conduit15 branches off from the conduit 14 and leads to a thermostat valve 16,through which the coolant, arriving from the engine 10, can be aspirateddirectly by the coolant pump 12 via a conduit 17. When the coolant iscold, the thermostat valve 16 keeps the communication open between thebypass conduit 15 and the conduit 17 that leads to the coolant pump 12,so that the coolant leaving the engine is returned directly to theengine 10 without passing through the radiator 11.

A conduit 18, which coming from the radiator 11 is connected to thethermostat valve 16. As soon as the coolant flowing in via the bypassconduit 15 has reached a predetermined temperature, the thermostat valve16 begins to block off the bypass conduit and to open the conduit 18 tothe radiator 11, so that then, more and more coolant arriving from theradiator 11 reaches the intake side of the coolant pump 12 via conduit17. The thermostat valve 16 determines the quantities of coolant thatare delivered through the bypass conduit 15 and the conduit 18 to theradiator 11. The engine 10 is thus heated to obtain an operatingtemperature within a minimum of time.

From the engine outlet conduit 14, a conduit 19 branches off and leadsto a heat exchanger 20, which is a component of a passenger compartmentheating system for the vehicle. The coolant flowing out of the heatexchanger 20 is delivered to the thermostat valve 16.

Via a ventilation valve, not shown, a conduit 22 is connected to a pointat the highest level of the cooling system and leads to a pressureequalizing tank or vent 23 placed at or higher than this high point. Theconduit 22, shown in dot-dashed lines, conducts essentially air or steamto the tank and any liquid collecting in the tank 23 is returned to thecooling system via a conduit 24, that connects the tank 23 to theconnected cooling system intake side of the cooling system pump 12.

A normally empty heat insulated reservoir 25 is connected by a conduit26 to the intake side of the cooling system pump 12 and is of avolumetric capacity to hold substantially the entire quantity of coolantpresent in the cooling system, i.e., in the engine 10, the radiator 11,the heat exchanger 20, the thermostat valve 16, and the conduits 13, 14,15, 17, 18, 19 and 20. An electric-motor-driven pump 27 and anelectrically switchable valve 28 are disposed in the conduit 26.

When the engine 10 is shut off, the pump 27 is turned on, and itsoperation is maintained for a predetermined length of time. This lengthof time is calculated such that within it, substantially the entirequantity of coolant in the cooling system can be aspirated and pumped tothe reservoir 25, which until then is empty or in other words containsonly air. Upon activation of the electric motor of the pump 27, theelectrically actuated valve 28, which is, for example, a magnet valve,is also opened. The entire quantity of coolant is thus pumped into thereservoir 25, including the coolant in the radiator 11. The valve 28prevents backflow of the coolant. The air contained in the reservoir 25flows out via a conduit 29, which is connected to the pressureequalizing tank 23. In practice, it will be useful to dispose a blockingvalve 30 in this conduit 29; this valve is likewise electricallyswitchable and is opened and closed together with the valve 28. Whilethe coolant is being pumped out of the cooling system by the pump 27,replenishing air flows into the cooling system through the conduit 22.

Upon a start up of the engine 10, the valves 28 and 30 are opened. Thecooling system pump 12, which may be an electric motor pump, buttypically is operatively connected to the crankshaft of the engine 10,and which starts up with the engine 10, aspirates the coolant from thereservoir 25 and pumps it into the engine 10 and from there back intocirculation in the cooling system. The reservoir 25 is disposed at apoint located at a level higher than the cooling system pump 12, so thatthe coolant flows by gravity to the intake side of the pump 12. Thevalves 28, 30 close once the reservoir 25 has been emptied.

Preferably, a heat insulated, heavy-duty reservoir 25 is provided, suchas a conventional thermos container that provides sufficient insulationso that over 24 hours only a temperature drop from approximately 100° C.to 60° C. takes place.

Since all the reservoir coolant from the cooling system is transferredto the reservoir, a correspondingly high quantity of heat is availablefor subsequent preheating of the engine 10. Moreover, the advantage isattained that the heat exchanger 20 for the passenger compartmentheating system is also supplied with warm coolant upon a cold start ofthe engine 10, so that the temperature of the passenger compartmentrises rapidly.

In a modification of the embodiment shown, the reservoir is formed intwo sections or as two separate reservoirs with each section orreservoir alternatively connected with the pump 27, conduit 26 and valve28, with a switching valve (not shown) for switching operation from onesection or reservoir to the other. In this case, in a first stage, achamber is filled with the quantity of coolant drawn from the engine,after which a switchover is made, and in the second stage, the secondchamber is filled with coolant arriving from the radiator 11; thiscoolant is typically cooler than that arriving from the engine. Thisprevents the two quantities of coolant, which have different temperaturelevels from each other, from mixing.

An alternative preferred embodiment is illustrated in FIG. 2. Itincludes a cooling system for an internal combustion engine 10, aradiator 11, a coolant pump 12, a thermostat valve 16, and a heatexchanger 20 for the passenger compartment heating system of a vehicle,all similar to the embodiment of FIG. 1. This cooling system alsoincludes a pressure equalizing or vent tank 23 with the ventilationconduit 22 and the return conduit 24 as in the embodiment of FIG. 1.However, the heat exchanger 20 of the passenger compartment heatingsystem is not connected to the engine outlet conduit 14. Instead, via aseparate conduit 31, it is subjected to coolant flowing out of theengine 10. A switchable regulating valve 32 is disposed in the conduitfrom the heat exchanger 20 to the mixing chamber of the thermostat valve16.

Parallel to the heat exchanger 20 for the passenger compartment heatingsystem of the vehicle, a heat exchanger 33 for a transmission fluidcooling system is provided in the cooling system. Both coolant and thefluid for an automatic transmission 34 belonging to the engine 10 flowthrough this transmission fluid heat exchanger 33. A heat exchanger 35for the motor oil is also provided, and coolant from the engine and themotor oil flow through it as well.

In this design as well, a normally empty heat insulated reservoir 25 ais provided, whose volume is designed such that it can receive theentire quantity of coolant that is present in the cooling system,including the passenger compartment heating system, the transmissionfluid cooling system and the motor oil cooling system. The reservoir 25a is connected to the intake side of the coolant pump 12 via a conduit26, which pump 27 can be operated by an electric motor. The conduit 26also includes an electrically switchable valve 28, such as a magnetvalve. The reservoir is connected to the venting tank 23 via a conduit29 and a switchable valve 30.

Between the reservoir 25 a and the conduit 31 that leads to the heatexchanger 20 for the passenger compartment heating system and to theheat exchanger 33 for the transmission fluid, there is a conduit 36which includes a further switchable valve 37 and a pump 38 which can bedriven by an electric motor. A check valve, not shown, that blocks areturn flow into the engine 10 is provided in the conduit 31.

The triggering of the pump 27, the valves 28, 30, the valve 37 and thepump 38 is effected via a control unit 39. The control unit may be acontrol unit, especially designed for this purpose, for the storagesystem or a thermomanagement device or the overall engine control unit.This control unit 39 also triggers the regulating valve 32, whichcontrols the inflow to the heat exchanger 20 for the passengercompartment heating system for the vehicle.

When the engine 10 is switched off, the control unit 39 switches thepump 27 on and opens the valves 28 and 30. The coolant is pumpedpractically entirely into the reservoir 25 a, evacuating the coolingsystem. Air flows into the cooling system from the venting tank 23 viathe conduit 22. The air present in the reservoir 25 a flows into theventing tank 23 via the valve 30 and the conduit 29.

When the engine is switched on, the redelivery of the coolant to thecooling system can take place, in the manner already described inconjunction with FIG. 1. However, it is also possible to proceed in astaggered delay sequence and, for instance, by means of the control unit39, first to open the valve 37 and to switch on the pump 38, such thatfirst hot coolant is pumped into the heat exchanger 20 and the heatexchanger 33 and from there flows to the engine 10. The valve 30 isopened so that replenishing air can flow into the reservoir 25 a. Thevalve 28 can be opened later, so that coolant is pumped out of thereservoir 25 a into the engine 10 and from there into the radiator 11with a delay after when the engine 10 is switched on.

For moderating the temperature of an internal combustion engine, inaddition to the described method, it may be provided that upon shut offof the engine, the entire quantity of motor oil in the engine is pumpedinto a hot oil reservoir which until then is empty or in other wordscontains air. Upon a start of the engine, the motor oil is then pumpedback into the engine, that is, into an oil cooler and the oil coolingconduits. The oil cooler may be a heat exchanger that is acted upon byair or preferably it may be a heat exchanger acted upon by the coolantfluid of the engine. The hot oil reservoir is disposed in a branch ofthe oil circulation and includes an electric-motor-driven oil pump. Thebranch is expediently connected to the intake side of the oil pump, thelatter being part of the oil circulation. The hot oil reservoir issuitably disposed at a point which is at a higher level than the oilpump of the oil circulation system.

In view of the aforesaid written description of the present invention,it will be readily understood by those persons skilled in the art thatthe present invention is susceptible of broad utility and application.Many embodiments and adaptations of the present invention other thanthose herein described, as well as many variations, modifications, andequivalent arrangements, will be apparent from or reasonably suggestedby the present invention and the foregoing description thereof, withoutdeparting from the substance or scope of the present invention.Accordingly, while the present invention has been described herein indetail in relation to preferred embodiments, it is to be understood thatthis disclosure is only illustrative and exemplary of the presentinvention and is made merely for purposes of providing a full andenabling disclosure of the invention. The foregoing disclosure is notintended nor is to be construed to limit the present invention orotherwise to exclude any such other embodiments, adaptations,variations, modifications and equivalent arrangements, the presentinvention being limited only by the claims appended hereto and theequivalents thereof.

1. A method of moderating the temperature of an internal combustionengine of a motor vehicle during start up of the engine after the enginehad previously been shut off, using a cooling system that circulatesliquid coolant through the engine, and a normally empty heat-insultedreservoir, said method comprising feeding the liquid coolant from thecooling system to the reservoir upon shut off of the engine, uponsubsequent start up of the engine feeding the coolant from the reservoirto the cooling system.
 2. The method of claim 1 characterized by saidfeeding the liquid coolant to the reservoir feeds substantially all ofthe liquid coolant from the cooling system to the reservoir.
 3. Themethod of claim 1 characterized by temporarily delaying the feed ofcoolant to the reservoir after the engine is shut off.
 4. The method ofclaim 1 characterized by temporarily delaying the feed of coolant fromthe reservoir to the cooling system upon start up of the engine.
 5. Themethod of claim 1, characterized by said feeding of the liquid coolantto the reservoir includes feeding liquid from at least one of apassenger compartment heating system, a transmission fluid coolingsystem and a motor oil cooling system, and said feeding of liquid fromsaid reservoir includes feeding said liquid to said at least one of apassenger compartment heating system, transmission fluid cooling systemand motor oil cooling system.
 6. The method of claim 5 characterized bysaid feeding liquid from said reservoir feeds in a staggered delaysequence.
 7. The method of claim 1 characterized by said feeding ofliquid from the reservoir to the cooling system temporarily bypasses aradiator of the engine cooling system.
 8. The method of claim 1characterized by the reservoir being formed in two separate sections ortwo separate reservoirs, and said feeding the liquid coolant feedscoolant from the engine through the cooling system to one of saidsections or reservoirs and feeds coolant from the radiator through thecooling system to the other of said sections or reservoirs.
 9. In acooling system for an internal combustion engine of a motor vehiclehaving a cooling system conduit through which liquid coolant iscirculated between a radiator and the engine, a reservoir systemcomprising a normally empty heat-insulating reservoir, a reservoirconduit connecting said cooling system conduit with said reservoir, apump in said reservoir conduit operable upon shut off of the engine tofeed the liquid coolant from said cooling system into said reservoir,and a valve in said reservoir conduit operable upon start up of saidengine for feed of the liquid coolant from said reservoir into saidcooling system.
 10. The reservoir system of claim 9 characterized bysaid reservoir having a capacity for containing substantially all of theliquid coolant in said cooling system.
 11. The reservoir system of claim9 characterized by a return conduit connecting said reservoir to atleast one of a passenger compartment heating system, a transmissionfluid cooling system and a motor oil cooling system for feeding liquidcoolant from said reservoir to said at least one said passengercompartment heating system, said transmission fluid cooling system andsaid motor oil cooling system.
 12. The reservoir system of claim 11characterized by said reservoir having a capacity for containingsubstantially all of the liquid coolant in said cooling system and saidat least one said passenger compartment heating system, saidtransmission fluid heating system and said motor oil cooling system. 13.The reservoir system of claim 11 characterized by a pump and a normallydosed valve in said return conduit operable upon start up of the engineto feed coolant liquid from said reservoir to said at least onepassenger compartment heating system, transmission fluid cooling systemand motor oil cooling system.
 14. The reservoir system of claim 9characterized by a temperature sensitive bypass control valve in saidcooling system conduit upstream of said radiator and sensitive to thetemperature of the cooling liquid to selectively divert the flow ofcoolant liquid to bypass the radiator and recirculate the cooling liquidto the engine.
 15. The reservoir system of claim 9 characterized by saidreservoir being positioned at a level higher than said radiator and saidengine for feed of cooling liquid from said reservoir to the coolingsystem by gravity.
 16. The reservoir system of claim 9 characterized bya valve in said reservoir conduit normally permitting flow of liquidcoolant to said reservoir and preventing backflow, and operable uponstart up of said engine to permit backflow of liquid coolant from saidreservoir to said cooling system.
 17. The reservoir system of claim 9characterized by said reservoir conduit being connected to said coolingsystem conduit upstream of a cooling system pump that pumps coolant tothe engine.
 18. The reservoir system of claim 9 characterized by saidreservoir being connected to a pressure equalizing tank of the coolingsystem for passage of air thereto from said reservoir as coolant liquidis fed to said reservoir.
 19. The reservoir system of claim 8characterized by said reservoir being formed in two separate sections ortwo separate reservoirs and said reservoir conduit being operable tofeed coolant alternatively to one or the other of said sections orreservoirs.